Smoke rises over Kobani following the strikes But US Central Command told Reuters there was no evidence to back up the report. Its forces use mitigation measures to reduce the potential for civilian casualties, a spokesman said.

The Syrian Observatory said Isis had launched at least 21 mortar attacks close to the border by Saturday afternoon.

In Kobani, a commander for the YPG, the Syrian Kurdish militia defending Kobani, said Isis's renewed attacks were aimed at severing the town's last link with Turkey.

"They want to cut off Kobani's connection with the rest of the world," she told Reuters by telephone. "Turkey is not allowing in fighters or weapons, but they send aid at Mursitpinar. Isis wants to destroy this gate so that we will be completely trapped here."

Strikes rock Kobani in Syria A cloud of black smoke towered over the centre of Kobani following the latest air strike as the roar of fighter jets could be heard from a blue sky. Gunfire popped in the west and centre of town.